Decoupled mode for a common uplink burst transmission in a time division duplex subframe structure

ABSTRACT

Various aspects of the present disclosure provide for methods, apparatus, and computer software for transmitting a common uplink burst in time division duplex (TDD) carriers. The common uplink burst includes a sounding reference signal (SRS) transmitted separate from (e.g., decoupled from) a demodulation reference signal (DM-RS). At least one symbol in the common uplink burst includes a control region for carrying control information and a data region for carrying data information. The SRS may be precoded separately from precoding of the control and data regions, so that the control and/or data information may be transmitted utilizing multiple input multiple output (MIMO).

PRIORITY CLAIM

This application claims priority to and the benefit of provisionalpatent application No. 62/265,313 filed in the United States Patent andTrademark Office on Dec. 9, 2015, the entire content of which isincorporated herein by reference as if fully set forth below in itsentirety and for all applicable purposes.

TECHNICAL FIELD

Aspects of the present disclosure relate generally to wirelesscommunication systems, and more particularly, to the channel structurefor uplink transmissions in a time division duplex (TDD) subframe.

INTRODUCTION

Wireless communication networks are widely deployed to provide variouscommunication services such as telephony, video, data, messaging,broadcasts, and so on. Such networks, which are usually multiple accessnetworks, support communications for multiple users by sharing theavailable network resources.

Within such wireless networks a variety of data services may beprovided, including voice, video, and emails. More recently, wirelesscommunication networks are being utilized for an even broader range ofservices, including mission critical applications and remote controlapplications such as tele-surgery, where real-time feedback isnecessary. In such applications, very low latency is critical to enablea suitably high quality of service. That is, the time for information tobe transmitted from a communication device, and a response received backat the communication device, may need to be extremely rapid, on theorder of milliseconds.

As the demand for mobile broadband access continues to increase,research and development continue to advance wireless communicationtechnologies not only to meet the growing demand for mobile broadbandaccess, but to advance and enhance the user experience.

BRIEF SUMMARY OF SOME EXAMPLES

The following presents a simplified summary of one or more aspects ofthe present disclosure, in order to provide a basic understanding ofsuch aspects. This summary is not an extensive overview of allcontemplated features of the disclosure, and is intended neither toidentify key or critical elements of all aspects of the disclosure norto delineate the scope of any or all aspects of the disclosure. Its solepurpose is to present some concepts of one or more aspects of thedisclosure in a simplified form as a prelude to the more detaileddescription that is presented later.

Various aspects of the present disclosure provide for methods,apparatus, and computer software for wireless communication utilizing acommon uplink burst, by employing a decoupled mode.

One aspect of the disclosure provides a method operable at a subordinateentity for wireless communication over a time division duplex (TDD)carrier. According the method, a subordinate entity transmits an uplinkburst within a downlink-centric subframe and an uplink-centric subframeon the TDD carrier. The uplink burst includes a first symbol and asecond symbol. The first symbol includes a sounding reference signal(SRS) configured to enable sounding of the TDD carrier. The secondsymbol includes information bits and a demodulation reference signal(DM-RS). The DM-RS is configured to enable demodulation of theinformation bits carried within the second symbol.

Another aspect of the disclosure provides a subordinate entityconfigured for wireless communication over a TDD carrier. Thesubordinate includes a processor, a memory communicatively coupled tothe processor, and a transceiver communicatively coupled to theprocessor. The processor and the memory are configured to transmit anuplink burst within a downlink-centric subframe and an uplink-centricsubframe on the TDD carrier. The uplink burst includes a first symboland a second symbol. The first symbol includes an SRS configured toenable sounding of the TDD carrier. The second symbol includesinformation bits and a DM-RS. The DM-RS is configured to enabledemodulation of the information bits carried within the second symbol.

Another aspect of the disclosure provides a subordinate entityconfigured for wireless communication over a TDD carrier. Thesubordinate entity includes means for transmitting an uplink burstwithin a downlink-centric subframe and an uplink-centric subframe on theTDD carrier. The uplink burst includes a first symbol and a secondsymbol. The first symbol includes an SRS configured to enable soundingof the TDD carrier. The second symbol includes information bits and aDM-RS. The DM-RS is configured to enable demodulation of the informationbits carried within the second symbol.

These and other aspects of the invention will become more fullyunderstood upon a review of the detailed description, which follows.Other aspects, features, and embodiments of the present invention willbecome apparent to those of ordinary skill in the art, upon reviewingthe following description of specific, exemplary embodiments of thepresent invention in conjunction with the accompanying figures. Whilefeatures of the present invention may be discussed relative to certainembodiments and figures below, all embodiments of the present inventioncan include one or more of the advantageous features discussed herein.In other words, while one or more embodiments may be discussed as havingcertain advantageous features, one or more of such features may also beused in accordance with the various embodiments of the inventiondiscussed herein. In similar fashion, while exemplary embodiments may bediscussed below as device, system, or method embodiments it should beunderstood that such exemplary embodiments can be implemented in variousdevices, systems, and methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communication networkaccording to some embodiments of the disclosure.

FIG. 2 is a schematic block diagram illustrating a scheduling entity incommunication with a plurality of subordinate entities according to someembodiments of the disclosure.

FIG. 3 is a block diagram illustrating an example of a wirelesscommunication device according to some embodiments of the disclosure.

FIG. 4 is a block diagram illustrating further detail of a schedulingentity in communication with a subordinate entity according to someembodiments of the disclosure.

FIG. 5 is a schematic diagram illustrating a downlink-centric subframeand an uplink-centric subframe each including a common uplink burstaccording to some embodiments of the disclosure.

FIG. 6 is a schematic diagram illustrating a structure of a commonuplink burst in a decoupled mode according to some embodiments of thedisclosure.

FIG. 7 is a schematic diagram illustrating a structure of a commonuplink burst in a decoupled mode according to some embodiments of thedisclosure.

FIG. 8 is a signal flow diagram illustrating subordinate entitiesrequesting resources in a common uplink (UL) burst from a schedulingentity according to some embodiments of the disclosure.

FIG. 9 is a diagram illustrating a method of operating a subordinateentity for wireless communication over a time division duplex (TDD)carrier in accordance with an aspect of the disclosure.

FIG. 10 is a diagram illustrating a precoding method of a soundingreference signal (SRS) and a demodulation reference signal (DM-RS) inaccordance with an aspect of the disclosure.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of various configurations and isnot intended to represent the only configurations in which the conceptsdescribed herein may be practiced. The detailed description includesspecific details for the purpose of providing a thorough understandingof various concepts. However, it will be apparent to those skilled inthe art that these concepts may be practiced without these specificdetails. In some instances, well known structures and components areshown in block diagram form in order to avoid obscuring such concepts.

The various concepts presented throughout this disclosure may beimplemented across a broad variety of telecommunication systems, networkarchitectures, and communication standards. Referring now to FIG. 1, asan illustrative example without limitation, a simplified schematicillustration of an access network 100 is provided.

The geographic region covered by the access network 100 may be dividedinto a number of cellular regions (cells), including macrocells 102,104, and 106, and a small cell 108, each of which may include one ormore sectors. Cells may be defined geographically (e.g., by coveragearea) and/or may be defined in accordance with a frequency, scramblingcode, etc. In a cell that is divided into sectors, the multiple sectorswithin a cell can be formed by groups of antennas with each antennaresponsible for communication with mobile devices in a portion of thecell.

In general, a radio transceiver apparatus serves each cell. A radiotransceiver apparatus is commonly referred to as a base station (BS) inmany wireless communication systems, but may also be referred to bythose skilled in the art as a base transceiver station (BTS), a radiobase station, a radio transceiver, a transceiver function, a basicservice set (BSS), an extended service set (ESS), an access point (AP),a Node B, an eNode B, or some other suitable terminology.

In FIG. 1, two high-power base stations 110 and 112 are shown in cells102 and 104; and a third high-power base station 114 is showncontrolling a remote radio head (RRH) 116 in cell 106. In this example,the cells 102, 104, and 106 may be referred to as macrocells, as thehigh-power base stations 110, 112, and 114 support cells having a largesize. Further, a low-power base station 118 is shown in the small cell108 (e.g., a microcell, picocell, femtocell, home base station, homeNode B, home eNode B, etc.) which may overlap with one or moremacrocells. In this example, the cell 108 may be referred to as a smallcell, as the low-power base station 118 supports a cell having arelatively small size. Cell sizing can be done according to systemdesign as well as component constraints. It is to be understood that theaccess network 100 may include any number of wireless base stations andcells. The base stations 110, 112, 114, 118 provide wireless accesspoints to a core network for any number of mobile apparatuses.

FIG. 1 further includes a quadcopter or drone 120, which may beconfigured to function as a base station. That is, in some examples, acell may not necessarily be stationary, and the geographic area of thecell may move according to the location of a mobile base station such asthe quadcopter 120.

In some examples, the base stations may be interconnected to one anotherand/or to one or more other base stations or network nodes (not shown)in the access network 100 through various types of backhaul interfacessuch as a direct physical connection, a virtual network, or the likeusing any suitable transport network.

The access network 100 is illustrated supporting wireless communicationfor multiple mobile apparatuses. A mobile apparatus is commonly referredto as user equipment (UE) in standards and specifications promulgated bythe 3rd Generation Partnership Project (3GPP), but may also be referredto by those skilled in the art as a mobile station (MS), a subscriberstation, a mobile unit, a subscriber unit, a wireless unit, a remoteunit, a mobile device, a wireless device, a wireless communicationsdevice, a remote device, a mobile subscriber station, an access terminal(AT), a mobile terminal, a wireless terminal, a remote terminal, ahandset, a terminal, a user agent, a mobile client, a client, or someother suitable terminology.

Within the present document, a “mobile” apparatus need not necessarilyhave a capability to move, and may be stationary. Some non-limitingexamples of a mobile apparatus include a mobile, a cellular (cell)phone, a smart phone, a session initiation protocol (SIP) phone, alaptop, a personal computer (PC), a notebook, a netbook, a smartbook, atablet, and a personal digital assistant (PDA). A mobile apparatus mayadditionally be an “Internet of things” (IoT) device such as anautomotive or other transportation vehicle, a satellite radio, a globalpositioning system (GPS) device, a logistics controller, a drone, amulti-copter, a quad-copter, a smart energy or security device, a solarpanel or solar array, municipal lighting, water, or otherinfrastructure; industrial automation and enterprise devices; consumerand wearable devices, such as eyewear, a wearable camera, a smart watch,a health or fitness tracker, a digital audio player (e.g., MP3 player),a camera, a game console, etc.; and digital home or smart home devicessuch as a home audio, video, and multimedia device, an appliance, asensor, a vending machine, intelligent lighting, a home security system,a smart meter, etc.

Within the access network 100, the cells may include UEs that may be incommunication with one or more sectors of each cell. For example, UEs122 and 124 may be in communication with base station 110; UEs 126 and128 may be in communication with base station 112; UEs 130 and 132 maybe in communication with base station 114 by way of RRH 116; UE 134 maybe in communication with low-power base station 118; and UE 136 may bein communication with mobile base station 120. Here, each base station110, 112, 114, 118, and 120 may be configured to provide an access pointto a core network (not shown) for all the UEs in the respective cells.

In another example, the quadcopter 120 may be configured to function asa UE. For example, the quadcopter 120 may operate within cell 102 bycommunicating with base station 110.

The air interface in the access network 100 may utilize one or moremultiplexing and multiple access algorithms to enable simultaneouscommunication of the various devices. For example, multiple access foruplink (UL) or reverse link transmissions from UEs 122 and 124 to basestation 110 may be provided utilizing time division multiple access(TDMA), code division multiple access (CDMA), frequency divisionmultiple access (FDMA), orthogonal frequency division multiple access(OFDMA), or other suitable multiple access schemes. Further,multiplexing downlink (DL) or forward link transmissions from the basestation 110 to UEs 122 and 124 may be provided utilizing time divisionmultiplexing (TDM), code division multiplexing (CDM), frequency divisionmultiplexing (FDM), orthogonal frequency division multiplexing (OFDM),or other suitable multiplexing schemes.

Within the access network 100, during a call with a scheduling entity,or at any other time, a UE may monitor various parameters of the signalfrom its serving cell as well as various parameters of neighboringcells. Further, depending on the quality of these parameters, the UE maymaintain communication with one or more of the neighboring cells. Duringthis time, if the UE moves from one cell to another, or if signalquality from a neighboring cell exceeds that from the serving cell for agiven amount of time, the UE may undertake a handoff or handover fromthe serving cell to the neighboring (target) cell. For example, UE 124may move from the geographic area corresponding to its serving cell 102to the geographic area corresponding to a neighbor cell 106. When thesignal strength or quality from the neighbor cell 106 exceeds that ofits serving cell 102 for a given amount of time, the UE 124 may transmita reporting message to its serving base station 110 indicating thiscondition. In response, the UE 124 may receive a handover command, andthe UE may undergo a handover to the cell 106.

In some examples, access to the air interface may be scheduled, whereina scheduling entity (e.g., a base station) allocates resources forcommunication among some or all devices and equipment within its servicearea or cell. Within the present disclosure, as discussed further below,the scheduling entity may be responsible for scheduling, assigning,reconfiguring, and releasing resources for one or more subordinateentities. That is, for scheduled communication, subordinate entitiesutilize resources allocated by the scheduling entity.

Base stations are not the only entities that may function as ascheduling entity. That is, in some examples, a UE may function as ascheduling entity, scheduling resources for one or more subordinateentities (e.g., one or more other UEs). For example, UE 138 isillustrated communicating with UEs 140 and 142. In this example, the UE138 is functioning as a scheduling entity, and UEs 140 and 142 utilizeresources scheduled by the UE 138 for wireless communication. A UE mayfunction as a scheduling entity in a peer-to-peer (P2P) network, and/orin a mesh network. In a mesh network example, UEs 140 and 142 mayoptionally communicate directly with one another in addition tocommunicating with the scheduling entity 138.

Thus, in a wireless communication network with a scheduled access totime—frequency resources and having a cellular configuration, a P2Pconfiguration, and a mesh configuration, a scheduling entity and one ormore subordinate entities may communicate utilizing the scheduledresources. Referring now to FIG. 2, a block diagram illustrates ascheduling entity 202 and a plurality of subordinate entities 204. Here,the scheduling entity 202 may correspond to the base stations 110, 112,114, and 118. In additional examples, the scheduling entity 202 maycorrespond to the UE 138, the quadcopter 120, or any other suitable nodein the access network 100. Similarly, in various examples, thesubordinate entity 204 may correspond to the UE 122, 124, 126, 128, 130,132, 134, 136, 138, 140, and 142, or any other suitable node in theaccess network 100.

As illustrated in FIG. 2, the scheduling entity 202 may broadcast data206 to one or more subordinate entities 204 (the data may be referred toas downlink data). In accordance with certain aspects of the presentdisclosure, the term downlink may refer to a point-to-multipointtransmission originating at the scheduling entity 202. Broadly, thescheduling entity 202 is a node or device responsible for schedulingtraffic in a wireless communication network, including the downlinktransmissions and, in some examples, uplink data 210 from one or moresubordinate entities to the scheduling entity 202. Another way todescribe the system may be to use the term broadcast channelmultiplexing. In accordance with aspects of the present disclosure, theterm uplink may refer to a point-to-point transmission originating at asubordinate entity 204. Broadly, the subordinate entity 204 is a node ordevice that receives scheduling control information, including but notlimited to scheduling grants, synchronization or timing information, orother control information from another entity in the wirelesscommunication network such as the scheduling entity 202.

The scheduling entity 202 may broadcast a control channel 208 to one ormore subordinate entities 204. Uplink data 210 and/or downlink data 206may be transmitted using a transmission time interval (TTI). Here, a TTImay correspond to an encapsulated set or packet of information capableof being independently decoded. In various examples, TTIs may correspondto frames, subframes, data blocks, time slots, or other suitablegroupings of bits for transmission.

Furthermore, the subordinate entities 204 may transmit uplink controlinformation 212 to the scheduling entity 202. Uplink control informationmay include a variety of packet types and categories, including pilots,reference signals, and information configured to enable or assist indecoding uplink data transmissions. In some examples, the controlinformation 212 may include a scheduling request (SR), i.e., request forthe scheduling entity 202 to schedule uplink transmissions. Here, inresponse to the SR transmitted on the control channel 212, thescheduling entity 202 may transmit in the downlink control channel 208information that may schedule the TTI for uplink packets. In a furtherexample, the uplink control channel 212 may include hybrid automaticrepeat request (HARQ) feedback transmissions, such as an acknowledgment(ACK) or negative acknowledgment (NACK). HARQ is a technique well-knownto those of ordinary skill in the art, wherein packet transmissions maybe checked at the receiving side for accuracy, and if confirmed, an ACKmay be transmitted, whereas if not confirmed, a NACK may be transmitted.In response to a NACK, the transmitting device may send a HARQretransmission, which may implement chase combining, incrementalredundancy, etc.

The channels illustrated in FIG. 2 are not necessarily all of thechannels that may be utilized between a scheduling entity 202 andsubordinate entities 204, and those of ordinary skill in the art willrecognize that other channels may be utilized in addition to thoseillustrated, such as other data, control, and feedback channels.

FIG. 3 is a conceptual diagram illustrating an example of a hardwareimplementation for a wireless communication device 300 employing aprocessing system 314. In accordance with various aspects of thedisclosure, an element, or any portion of an element, or any combinationof elements may be implemented with a processing system 314 thatincludes one or more processors 304. For example, the wirelesscommunication device 300 may be a scheduling entity 202, base station(BS) 102, or any other suitable network node, as illustrated in FIGS. 1,2, 4, and/or 8. Furthermore, the wireless communication device 300 maybe a subordinate entity 204, a UE 126 or 128, an IoE device, or anyother suitable network node, as illustrated in FIGS. 1, 2, 4, and/or 8.Examples of processors 304 include microprocessors, microcontrollers,digital signal processors (DSPs), field programmable gate arrays(FPGAs), programmable logic devices (PLDs), state machines, gated logic,discrete hardware circuits, and other suitable hardware configured toperform the various functionality described throughout this disclosure.That is, the processor 304, as utilized in a wireless communicationdevice 300, may be used to implement any one or more of the processesdescribed in the present disclosure.

In this example, the processing system 314 may be implemented with a busarchitecture, represented generally by the bus 302. The bus 302 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the processing system 314 and the overall designconstraints. The bus 302 links together various circuits including oneor more processors (represented generally by the processor 304), amemory 305, and computer-readable media (represented generally by thecomputer-readable medium 306). The bus 302 may also link various othercircuits such as timing sources, peripherals, voltage regulators, andpower management circuits, which are well known in the art, andtherefore, will not be described any further. A bus interface 308provides an interface between the bus 302 and one or more transceivers310. The transceivers 310 provide a communication interface or means forcommunicating with various other apparatus over a transmission medium.In various examples, the transceivers 310 may include one or moreantennas, and in multi-antenna examples, may be enabled to determine anangle from which a received signal arrives, or for beamforming oftransmitted signals. The transceiver 310 may include varioussub-components configured to enable wireless communication, includingbut not limited to one or more power amplifiers, a transmitter, areceiver, filters, oscillators, etc. Further, depending upon the natureof the apparatus, a user interface 312 (e.g., keypad, display, speaker,microphone, joystick, etc.) may also be provided.

In some aspects of the disclosure, the processor 304 may include acommon uplink (UL) burst block 320 that can be configured to performvarious functions for a common UL burst described in relation to FIGS.5-10. For example, the common UL burst block 320 may include one or morefunctional blocks or components, for example, a DL-centric subframeblock 322, an UL centric subframe block 324, a control information block326, a data information block 328, a demodulation reference signal(DM-RS) block 330, and a sounding reference signal (SRS) block 332. Thecommon UL burst block 320 may be configured by executing code, forexample, common UL burst communication code stored in thecomputer-readable medium 306.

The DL-centric subframe block 322 may be configured to perform functionsfor handling DL-centric subframe communication: for example,transmitting, receiving, and/or scheduling one or more DL-centricsubframes 504 (see FIG. 5). The UL-centric subframe block 324 may beconfigured to perform functions for handling UL-centric subframecommunication: for example, transmitting, receiving, and/or schedulingone or more UL-centric subframes 502 (see FIG. 5). The controlinformation block 326 may be configured to handle control information,for example, transmitting, receiving, and/or scheduling a schedulingrequest (SR), an acknowledgment (ACK)/negative acknowledgment (NACK),and other control signals in a common UL burst. The data informationblock 328 may be configured to handle data information, for example,transmitting, receiving, and/or scheduling a physical uplink sharedchannel (PUSCH) or other user data. The DM-RS block 330 may beconfigured to perform functions related to the DM-RS as described inrelation to FIGS. 5-10. The SRS block 332 may be configured to performfunctions related to the SRS as described in relation to FIGS. 5-10.

The processor 304 is responsible for managing the bus 302 and generalprocessing, including the execution of software stored on thecomputer-readable medium 306. The software, when executed by theprocessor 304, causes the processing system 314 to perform the variousfunctions described below for any particular apparatus. Thecomputer-readable medium 306 may also be used for storing data that ismanipulated by the processor 304 when executing software.

One or more processors 304 in the processing system may executesoftware. Software shall be construed broadly to mean instructions,instruction sets, code, code segments, program code, programs,subprograms, software modules, applications, software applications,software packages, routines, subroutines, objects, executables, threadsof execution, procedures, functions, etc., whether referred to assoftware, firmware, middleware, microcode, hardware descriptionlanguage, or otherwise. The software may reside on a computer-readablemedium 306. The computer-readable medium 306 may be a non-transitorycomputer-readable medium. A non-transitory computer-readable mediumincludes, by way of example, a magnetic storage device (e.g., hard disk,floppy disk, magnetic strip), an optical disk (e.g., a compact disc (CD)or a digital versatile disc (DVD)), a smart card, a flash memory device(e.g., a card, a stick, or a key drive), a random access memory (RAM), aread only memory (ROM), a programmable ROM (PROM), an erasable PROM(EPROM), an electrically erasable PROM (EEPROM), a register, a removabledisk, and any other suitable medium for storing software and/orinstructions that may be accessed and read by a computer. Thecomputer-readable medium 306 may reside in the processing system 314,external to the processing system 314, or distributed across multipleentities including the processing system 314. The computer-readablemedium 306 may be embodied in a computer program product. By way ofexample, a computer program product may include a computer-readablemedium in packaging materials. Those skilled in the art will recognizehow best to implement the described functionality presented throughoutthis disclosure depending on the particular application and the overalldesign constraints imposed on the overall system.

FIG. 4 is a block diagram showing additional details of one example of ascheduling entity 202 in communication with one example of a subordinateentity 204 in an access network. In the DL, upper layer packets from thecore network are provided to a controller/processor 475. Thecontroller/processor 475 implements the functionality of the L2 layer.In the DL, the controller/processor 475 provides header compression,ciphering, packet segmentation and reordering, multiplexing betweenlogical and transport channels, and radio resource allocations to thesubordinate entity 204 based on various priority metrics. Thecontroller/processor 475 is also responsible for hybrid automatic repeatrequest (HARQ) operations, retransmission of lost packets, and signalingto the subordinate entity 204.

The transmit (TX) processor 416 implements various signal processingfunctions for the L1 layer (i.e., physical layer). The signal processingfunctions include coding and interleaving to facilitate forward errorcorrection (FEC) at the subordinate entity 204 and mapping to signalconstellations based on various modulation schemes (e.g., binaryphase-shift keying (BPSK), quadrature phase-shift keying (QPSK),M-phase-shift keying (M-PSK), M-quadrature amplitude modulation(M-QAM)). The coded and modulated symbols are then split into parallelstreams. Each stream is then mapped to an OFDM subcarrier, multiplexedwith a reference signal (e.g., pilot) in the time and/or frequencydomain, and then combined together using an Inverse Fast FourierTransform (IFFT) to produce a physical channel carrying a time domainOFDM symbol stream. The OFDM stream is spatially precoded to producemultiple spatial streams. Channel estimates from a channel estimator 474may be used to determine the coding and modulation scheme, as well asfor spatial processing. The channel estimate may be derived from areference signal and/or channel condition feedback transmitted by thesubordinate entity 204. Each spatial stream may then be provided to adifferent antenna 420 via a separate transmitter 418TX. Each transmitter418TX may modulate a radio frequency (RF) carrier with a respectivespatial stream for transmission.

At the subordinate entity 204, each receiver 454RX receives a signalthrough its respective antenna 452. Each receiver 454RX recoversinformation modulated onto an RF carrier and provides the information tothe receive (RX) processor 456. The RX processor 456 implements varioussignal processing functions of the L1 layer. The RX processor 456 mayperform spatial processing on the information to recover any spatialstreams destined for the subordinate entity 204. If multiple spatialstreams are destined for the subordinate entity 204, they may becombined by the RX processor 456 into a single OFDM symbol stream. TheRX processor 456 then converts the OFDM symbol stream from thetime-domain to the frequency domain using a Fast Fourier Transform(FFT). The frequency domain signal comprises a separate OFDM symbolstream for each subcarrier of the OFDM signal. The symbols on eachsubcarrier, and the reference signal, are recovered and demodulated bydetermining the most likely signal constellation points transmitted bythe scheduling entity 202. These soft decisions may be based on channelestimates computed by the channel estimator 458. The soft decisions arethen decoded and deinterleaved to recover the data and control signalsthat were originally transmitted by the scheduling entity 20 on thephysical channel. The data and control signals are then provided to thecontroller/processor 459.

The controller/processor 459 implements the L2 layer. Thecontroller/processor can be associated with a memory 460 that storesprogram codes and data. The memory 460 may be referred to as acomputer-readable medium. In the UL, the controller/processor 459provides demultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the core network. The upper layerpackets are then provided to a data sink 462, which represents all theprotocol layers above the L2 layer. Various control signals may also beprovided to the data sink 462 for L3 processing. Thecontroller/processor 459 is also responsible for error detection usingan acknowledgement (ACK) and/or negative acknowledgement (NACK) protocolto support HARQ operations.

In the UL, a data source 467 is used to provide upper layer packets tothe controller/processor 459. The data source 467 represents allprotocol layers above the L2 layer. Similar to the functionalitydescribed in connection with the DL transmission by the schedulingentity 202, the controller/processor 459 implements the L2 layer for theuser plane and the control plane by providing header compression,ciphering, packet segmentation and reordering, and multiplexing betweenlogical and transport channels based on radio resource allocations bythe scheduling entity 202. The controller/processor 459 is alsoresponsible for HARQ operations, retransmission of lost packets, andsignaling to the scheduling entity 202.

Channel estimates derived by a channel estimator 458 from a referencesignal or feedback transmitted by the scheduling entity 202 may be usedby the TX processor 468 to select the appropriate coding and modulationschemes, and to facilitate spatial processing. The spatial streamsgenerated by the TX processor 468 may be provided to different antenna452 via separate transmitters 454TX. Each transmitter 454TX may modulatean RF carrier with a respective spatial stream for transmission.

The UL transmission is processed at the scheduling entity 202 in amanner similar to that described in connection with the receiverfunction at the subordinate entity 204. Each receiver 418RX receives asignal through its respective antenna 420. Each receiver 418RX recoversinformation modulated onto an RF carrier and provides the information toa RX processor 470. The RX processor 470 may implement the L1 layer.

The controller/processor 475 implements the L2 layer. Thecontroller/processor 475 can be associated with a memory 476 that storesprogram codes and data. The memory 476 may be referred to as acomputer-readable medium. In the UL, the control/processor 475 providesdemultiplexing between transport and logical channels, packetreassembly, deciphering, header decompression, control signal processingto recover upper layer packets from the subordinate entity 204. Upperlayer packets from the controller/processor 475 may be provided to thecore network. The controller/processor 475 is also responsible for errordetection using an ACK and/or NACK protocol to support HARQ operations.

Common UL Burst on a TDD Carrier

In any wireless communication network, bi-directional communication is adesirable feature. Frequently, duplexing communication onto the airchannel is accomplished utilizing frequency division duplex (FDD) ortime division duplex (TDD). In FDD, a pair of carriers are used, witheach respective carrier being used to carry communication signals in adifferent direction. In TDD, unpaired carriers are used. Here, duplexingof uplink and downlink communication is achieved by time sharing thecarrier, with uplink and downlink communication occupying the carrier atdifferent times.

In many modern wireless communication networks, significant portions ofthe spectrum have been allocated out by regulatory agencies in pairedcarriers for 1-DD. For new developing technologies, if very highbandwidth communication is desired (e.g., 100 MHz, 300 MHz, or more);however, these FDD technologies already utilize much of the spectrum,and may not be as wideband as desired for much higher data rates. Athigher frequencies, including but not limited to millimeter wave (mmW)frequencies, TDD carriers may be more available. Furthermore, such TDDcarriers may be less expensive for a carrier to obtain rights to use.

When utilizing a TDD carrier, communication may in some examples beorganized by dividing the channel in the time domain into frames, withframes being further divided into subframes. According to an aspect ofthe present disclosure, subframes may take at least two general forms,referred to herein as an uplink-centric subframe structure and adownlink-centric subframe structure. Here, a downlink-centric subframeis a subframe where a majority of its time is used for communication inthe downlink direction; and an uplink-centric subframe is a subframewhere a majority of its time is used for communication in the uplinkdirection.

FIG. 5 is a schematic illustration showing a set of subframes 500 (e.g.,a frame) including one uplink-centric subframe 502 every four subframes,with the remaining three out of four subframes being downlink-centricsubframes 504. Of course, this particular allocation ofuplink-to-downlink centric subframes is merely one example, and anyproportion of uplink and downlink centric subframes may be utilized in aparticular implementation.

In the illustrated examples, portions of each subframe utilized foruplink communication are called uplink portions 506, and portions ofeach subframe utilized for downlink communication are called downlinkportions 508. Here, a gap, a guard period, a guard interval, or a guardregion (not shown) may be utilized after a downlink portion and beforean uplink portion, or vice versa. Such a gap may facilitate switching orreconfiguration of the RF components, including re-tuning a phase-lockloop and other radio functions.

The illustrated downlink-centric subframe 504 includes a control region510, which may include a physical downlink control channel (PDCCH), anda data region 512, which may include a physical downlink shared channel(PDSCH). The control region 510 may include, among other things,scheduling information for informing scheduled devices (e.g.,subordinate entities) which resources in the data region 512 includeinformation for that particular device.

The illustrated uplink-centric subframe 502 also includes a controlregion 514, which may include a PDCCH, and a data region 516, which mayinclude a physical uplink shared channel (PUSCH) and/or other suitablechannels corresponding to an uplink data burst. The control region 514may include, among other things, scheduling information for informingscheduled devices (e.g., subordinate entities) which resources they mayutilize for uplink transmissions in the data region 516.

As illustrated in this example, both the uplink-centric subframe 502 andthe downlink-centric subframe 504 include a common uplink burst portion518. In this example, the common UL burst is shown at the end of eachsubframe, but it is not necessarily limited to the end, and in otherexamples the common UL burst 518 may appear at any suitable time withinan uplink-centric subframe 502 or a downlink-centric subframe 504,including at the beginning of the subframe, or anywhere within thesubframe. In some examples, the common UL burst 518 may be structured inthe same way in both the uplink-centric subframes and in thedownlink-centric subframes.

In an aspect of the disclosure, the common UL burst 518 may be arelatively short portion of the respective subframe, including, forexample, two or more symbols. For example, a two-symbol common UL burstmay have a duration of around 31 microsecond (μs). Of course, differentdurations, and different numbers of symbols may be included in thecommon UL burst within the scope of the present disclosure. That is, ina common UL burst within the scope of the present disclosure, anysuitable number of symbols (e.g., OFDM symbols) may be utilized.However, for clarity, within the present disclosure, a common UL burstincluding two symbols is described in further detail in relation toFIGS. 6 and 7 below.

Here, the common UL burst 518 may be utilized to decouple the latencyassociated with a control channel carried in the common UL burst, fromthe uplink/downlink pattern selected in any given implementation. Thatis, in a TDD scheme, the downlink-centric subframes may typically appearmuch more frequently than the uplink-centric subframes, because moreregular network traffic may typically be in the downlink direction.Further, in a typical deployment of a macrocell (e.g., an eNode B in anLTE deployment), this ratio between uplink and downlink traffic remainsrelatively stable over time. That is, even though any single user'sUL/DL ratio may change rather drastically, when aggregated over largenumbers of users, the overall ratio generally remains nearly the same.However, small cells, which unlike a macrocell, may only serve verysmall numbers of users, and the total ratio between UL and DL-centricsubframes can largely vary over time.

Thus, depending on the cell size and the loading of the cell, thedownlink and uplink patterns may change, and the ratio between uplinkand downlink-centric subframes may be any suitable ratio, fromone-to-one, or otherwise.

If the uplink-centric subframe is very rare, then, and downlink-centricsubframes dominate, there may be a problem in that a device withcritical or time-sensitive uplink information to transmit may need towait for an extended period of time until its uplink information can betransmitted in the uplink-centric subframe. In particular, controlinformation such as channel quality information and feedback (e.g.,packet acknowledgments) may have a time-sensitive nature, and theirrapid and timely transmission may be important. Therefore, including acommon UL burst region in each subframe or a majority (e.g., more than50%) of subframes, including the downlink-centric subframe, can helpreduce or avoid such an extended latency for time-sensitive packets.

In a further aspect of the disclosure, such a common UL burst schemeprovides for the same channel structure to be utilized in unlicensedbands as well as licensed bands. In unlicensed bands, users (e.g.,subordinate entities) typically compete for resources, and are only ableto reserve use of the channel for a limited time before giving up thechannel for other users. Here, if a transmission is received just at theend of the time when a user has the channel, and the device loses thechannel before having an opportunity to transmit an acknowledgment (orother time-critical uplink packet), the device may be required to waitfor an extended period to make such transmission, until the channel canbe re-acquired. However, with the common UL burst channel structure, aresource for such transmissions can be made available in every subframe,reducing or avoiding such a delay for time-critical transmissions.

The common UL burst may additionally or alternatively be utilized forthe transmission of other control information, such as a schedulingrequest (SR). A scheduling request may be an uplink transmission ofinformation requesting a scheduling entity (e.g., a base station or eNB)to schedule and/or allocate uplink channel resources for the scheduleddevice to utilize to transmit uplink data. These resources may appearwithin the regular UL burst region 506 illustrated in the uplink-centricsubframe 502.

In still another example, the common UL burst may additionally oralternatively be utilized to carry a sounding reference signal (SRS).Within an unpaired TDD spectrum, the channel that a scheduled device(e.g., a UE or subordinate entity) sees for downlink transmissions isthe same channel that a scheduling entity (e.g., an eNB) sees for uplinktransmissions. Therefore, channel characterization is somewhatsimplified relative to that for FDD channels. That is, the schedulingentity generally requires information about the downlink channel as seenby the receiving or subordinate entity in order to most suitablyschedule resources for that user. While in an FDD channel a UE measuresthe channel and sends feedback to the base station to report its channelconditions; in a TDD channel, the UE may transmit the SRS in an uplinktransmission, and the base station may utilize this transmission tocharacterize the channel on its own for scheduling downlinktransmissions. This SRS transmission is generally desired to betransmitted with low latency, i.e., its transmission is somewhat timecritical. Thus, placement of the SRS within the common UL burst region518 can decouple its latency from the downlink to uplink pattern or viceversa in a given implementation.

Of course, the above are merely examples, and within the scope of thepresent disclosure, the common UL burst may be utilized not only forsuch control information, but may additionally or alternatively beutilized to carry uplink payload data with a low latency requirement.Here, such uplink payload transmissions in the common UL burst regionmay be limited to transmitting devices having sufficient power headroomfor these transmissions.

Coupled Mode vs. Decoupled Mode

Referring once again to FIG. 1, a UE 126 is illustrated relatively farfrom the base station 112 (e.g., at or near a cell edge), while anotherUE 128 is illustrated relatively close to the base station 112 (e.g., ator near a cell center). As described further below, according to variousaspects of the present disclosure, users located at the cell centersimilar to the UE 128 may have sufficient power headroom to include datatransmissions in the common UL burst, while users located at the celledge similar to the UE 126 may lack the power headroom to include datatransmissions in the common UL burst. Accordingly, in various aspects ofthe disclosure, users at the cell edge may be configured to make theircommon UL burst transmissions in a coupled mode that facilitatescoverage extension for control information transmissions, while users ator near the cell center may be configured to make their common UL bursttransmissions in a decoupled mode that facilitates user datatransmissions in addition to control information transmissions

That is, these common UL burst regions within the subframes as describedabove may be configured to support all users and devices, includingusers near the cell center, as well as users near a cell edge. For usersat or near the cell edge, whose signal may be weak because they arerelatively far from the base station or scheduling entity, the contentof the information within the common UL burst region may be limited tocertain control information such as the packet acknowledgments (ACK) andscheduling requests (SR), which may be carried on a physical uplinkcontrol channel (PUCCH). For these users near or at the cell edge,transmissions may be made in a certain mode, referred to herein in thepresent disclosure as a coupled mode.

In the coupled mode, the SRS may be re-used or repurposed to serve thepurpose of the demodulation reference signal (DM-RS), so thatdemodulation of the information bits in the common UL burst may beaccomplished with the coupled SRS/DM-RS signal. That is, in coupled modetransmissions, the DM-RS (described further below, and illustrated inFIGS. 6 and 7) may be omitted. In this way, for coupled modetransmissions, the additional power that may be consumed by thetransmission of the DM-RS pilot may be conserved. Thus, coupled modetransmissions may have a reduced power consumption.

On the other hand, in a decoupled mode, which may be targeted for usersor devices that may be relatively close to the scheduling entity or basestation, because their signal may be more easily received by the basestation, these devices generally have sufficient power headroom toaccommodate the additional pilot transmissions associated with theDM-RS.

Therefore, if a user or device is relatively close to the cell center orclose to the base station or scheduling entity, it may be possible toaccumulate or supply enough energy even during the short common UL burstto include uplink payload data in this region. Accordingly, in an aspectof the present disclosure, the decoupled mode is provided, e.g., forthese users or devices that are relatively close to the cell center orclose to the base station or scheduling entity.

In the decoupled mode, the UE or subordinate entity may be enabled toopportunistically transmit uplink payload data having low latencyrequirements. That is, by virtue of the decoupled mode, devicesoperating in decoupled mode may be enabled to transmit information on aPUSCH within the common UL burst region of uplink-centric subframes anddownlink-centric subframes. The present disclosure refers specificallyto the PUSCH, however, it is to be understood that this term is merelyincluded for clarity, and aspects of the disclosure may utilize anysuitable physical uplink channel for carrying traffic payload data.

Within the present disclosure, the name “decoupled” with reference tothe decoupled mode generally refers to a decoupling of the SRS from ademodulation reference signal (DM-RS). In order to demodulate the PUCCHor PUSCH, a pilot or reference signal may be needed. Here, the DM-RSprovides a pilot that may be utilized to demodulate the PUCCH/PUSCHbits. In a decoupled mode, the SRS and the DM-RS are different symbols,and may have different transmission characteristics. Thus, the SRS andDM-RS are decoupled from one another and can be beamformed or precodeddifferently.

In some examples, because decoupled mode users may generally be thosethat are close to the scheduling entity or base station, those users mayutilize multiple-input multiple-output (MIMO) or other beamformingtechniques in their uplink transmissions.

That is, the subordinate entities 204 (e.g., UEs 128, wirelesscommunication devices 300, user equipment or UEs, etc.) may havemultiple antennas supporting Multiple Input Multiple Output (MIMO)technology. The use of MIMO technology enables the wirelesscommunication devices to exploit the spatial domain to support spatialmultiplexing, beam-forming, and transmit diversity. Spatial multiplexingmay be used to transmit different streams of data simultaneously on thesame frequency. The data streams may be transmitted to a singlereceiving device to increase the data rate or to multiple receivingdevices to increase the overall system capacity. This is achieved byspatially precoding each data stream (i.e., applying a scaling of anamplitude and a phase) and then transmitting each spatially precodedstream through multiple transmit antennas. The spatially pre-coded datastreams arrive at the receiving device(s) with different spatialsignatures, which enables each of the receiving devices to recover theone or more data streams destined for that device.

Spatial multiplexing is generally used when channel conditions are good.When channel conditions are less favorable, beamforming may be used tofocus the transmission energy in one or more directions. This may beachieved by spatially precoding the data for transmission throughmultiple antennas.

Specifically referring to the common UL burst, in order to use MIMO, thetransmitted information is suitably configured utilizing a certainprecoding matrix. That is, in an aspect of the present disclosure, toenable MIMO or beamforming for the uplink data within the common ULburst, the uplink data transmitted within this common UL burst may beprecoded utilizing a selected precoding matrix. In general, the selectedprecoding matrix maps data to the antennas for spatial multiplexingand/or beamforming.

However, in a further aspect of the disclosure, the SRS transmissionwithin the common UL burst may not be beamformed or precoded for MIMOtransmission. For users who wish to use MIMO in their uplinktransmissions, the pilot (i.e., the SRS) generally cannot be used as thedemodulation reference signal (DM-RS) for demodulating the data, sincethe data and the pilot use different precoding, and are accordinglybeamformed differently. Therefore, the SRS and its precoding orbeamforming is decoupled from the DM-RS and its precoding orbeamforming.

FIGS. 6 and 7 are schematic illustrations showing additional details ofthe common UL burst 518 as it may be structured for transmissions in thedecoupled mode, according to some aspects of the present disclosure.While these illustrations provide exemplary bandwidth figures, it willbe understood that the specific values for the bandwidth for the controlregion (illustrated as 10 MHz) and the data region (illustrated as 70MHz) are merely illustrative in nature, and any suitable bandwidth foreither region may be utilized in a particular implementation within thescope of the present disclosure. Furthermore, the location of thecontrol region and data region may vary from the illustrated examples.That is, while the illustrations show the control region at the top orupper portion of the resource block and the data region at the bottom orlower portion of the resource block, these can be rearranged within thescope of the disclosure. Furthermore, while the illustrations show thecontrol region and the data region each being fully contiguous, this isnot necessary, and within the scope of the disclosure, one or both ofthe control and/or data regions may be discontinuous, occupying two ormore separate portions of the resource block.

FIGS. 6 and 7 show two different optional formats for the common ULburst 518 in decoupled mode. In the first format, in FIG. 6, onlycontrol information 602 (e.g., ACK/SR) is carried in the common ULburst. In the second format, in FIG. 7, control information 702 (e.g.,ACK/SR) and data information 704 (e.g., PUSCH) are both carried in thecommon UL burst. In various aspects of the disclosure, decoupled modetransmissions may include control information within the control region,and any suitable amount of data within the data region. That is, in someaspects of the disclosure, in a common UL burst 518 configured fordecoupled mode, the control region may have a fixed bandwidth, while thedata region may have a variable bandwidth. For example, as in the firstexample in FIG. 6, a decoupled mode transmission may include no datainformation in the data region (i.e., no data region). In anotherexample, as in the second example in FIG. 7, a decoupled modetransmission may include sufficient data information in the data regionto completely fill all subcarriers in the data region. In otherexamples, any amount of data information between these examples may betransmitted in a particular common UL burst. As described in furtherdetail below, the exact bandwidth of the data region, and its allocationamong different users making common UL burst transmissions in decoupledmode, may be controlled by the scheduling entity (e.g., eNB) andcommunicated to the users or subordinate entities (e.g., UEs) utilizinga scheduling grant.

In some examples, a typical symbol may have a duration of about 30 μs orany suitable duration. However, in an aspect of the present disclosure,within the common UL burst, some symbols may be shortened relative toother symbols. As an example, in the illustrations of FIGS. 6 and 7, twoshort symbols (first symbol and second symbol) may be scaled to occupyaltogether only the 30 μs common UL burst region 518. However, asalready mentioned above, a common UL burst may include any suitablenumber of symbol periods, and any suitable scaling of symbols relativeto nominal symbol timing may be utilized.

In the illustrated examples, in FIGS. 6 and 7, the first symbol withinthe common UL burst may include a sounding reference signal (SRS) 604and 706, and the second symbol within the common UL burst may includecontrol (e.g., ACK/SR 602, 702) and/or data information (e.g., PUSCH704). The SRS is essentially a pilot transmitted by the scheduled device(e.g., a UE), to enable the base station or scheduling entity to sense(or sound) the channel for the purpose of configuring and schedulingdownlink transmissions.

Here, the SRS is illustrated as a wideband signal, taking up the entireband (or all subcarriers). This is merely one example though, and it maybe assumed that the transmitting subordinate entity (e.g., UE) cansupport such a transmission across the entire band or all subcarriers.Support of such a wideband transmission may be eased to some extent forUEs that are at or near the cell center. Transmission of the SRS in thiswideband format can enable the receiving device (e.g., the schedulingentity or eNB) to sound the channel in one shot, saving time relative tothe transmission of multiple SRSes in different portions or subcarriersof the band. In a further aspect of the disclosure, the SRS may be mixedor coded with a UE-specific scrambling code. In this way, the receivingscheduling entity (e.g., eNB) may be enabled to separate the SRStransmissions from different users or devices utilizing conventionalCDMA techniques, known to those of ordinary skill in the art.

The control and data information in the second symbol may include thePUCCH for carrying time- or latency-sensitive control information suchas packet acknowledgments (ACK), scheduling requests (SR), etc., and insome examples, the PUSCH for carrying uplink data. In the illustratedexample, the PUCCH and the PUSCH are separated from one another byfrequency. That is, these respective channels may befrequency-division-multiplexed within a single (one or more) symboldurations within the common UL burst. In this way, a transmission fromthe PUCCH/PUSCH of a high-power user may have less of an impact on thescheduling entity's reception of other users' transmissions of the PUSCHon different subcarriers.

As illustrated in FIGS. 6 and 7, the DM-RS pilot 606, 708 is showntaking every other subcarrier across the band. However, aspects of thepresent disclosure may utilize other configurations for the DM-RS, andthe DM-RS need not necessarily occupy half of the tones or subcarriersacross the band, and may occupy 25%, or any suitable proportion of theentire band.

In an aspect of the present disclosure, the PUCCH and the PUSCH may eachhave separate demodulation reference signals (DM-RS). That is, one pilotor DM-RS may be transmitted along with the control information bits inthe PUCCH, while a second pilot or DM-RS may be transmitted along withthe data information bits in the PUSCH. The illustration shows one setof DM-RS pilots being transmitted within every other subcarrier in thePUCCH (control) region, and another set of DM-RS pilots beingtransmitted within every other subcarrier in the PUSCH (data) region.However, as indicated above, other arrangements of the DM-RS within eachregion may vary from this example in a particular implementation.

In a still further aspect of the disclosure, for transmitting devicesthat include multiple antennas, such as those configured for beamformingand/or MIMO, each transmitting antenna may transmit its own DM-RS,different from the DM-RS transmitted by other antennas. That is, to bestfacilitate such uplink MIMO transmissions, the receiving device may needto differentiate different pilots (DM-RS signals) from differenttransmit antennas. According to an aspect of the present disclosure,code division multiplexing (CDM) may be utilized by the transmittingdevice (e.g. a UE or subordinate entity) to enable this differentiationbetween the pilots transmitted by different antennas. That is, thesepilots transmitted from two different antennas may be scrambled by twodifferent scrambling codes, and then transmitted at the same time, andwithin the same subcarrier. However, the receiving scheduling entity(e.g., eNB) is enabled to differentiate the different pilots from thedifferent transmit antennas utilizing conventional code-divisionmultiplexing procedures, well-known to those of ordinary skill in theart.

Within any given symbol, only a limited amount of resources areavailable to carry information. By taking some of the tones orsubcarriers out of the available resources to dedicate those tones orsubcarriers for pilot transmissions (e.g., SRS and DM-RS), even lessresources are available to be dedicated for data information. For thisreason, it is desired not to even further divide these resources toprovide for different pilot transmissions for each of multiple antennasfor uplink MIMO transmissions. Thus, when pilot tones such as the DM-RSare utilized, they may occupy the same time-frequency resources, but maybe differentiated utilizing different scrambling codes as describedabove.

If the scheduling entity (e.g., eNB) schedules two users (e.g. UEs) tosend the data information on the PUSCH, then these users may bescheduled, so that each of the users utilize designated resourcesidentified by the scheduling entity. This scheduling information may becommunicated to the users or subordinate entity utilizing schedulinggrants, which may be unicast or broadcast messages, or any othersuitable control channel transmission format configured to convey thescheduling grant. The scheduling grant may be carried in the PDCCH(e.g., PDCCH 510 and 514 of FIG. 5).

Further, referring to FIG. 8, when a subordinate entity (e.g., UE) hasUL data to transmit, and wishes to request resources on the PUSCH in thecommon UL burst, the subordinate entity may transmit a schedulingrequest (SR) 802 within the PUCCH region (see FIGS. 6 and 7) of thecommon UL burst. That is, in one subframe, within the common UL burst, asubordinate entity may transmit the scheduling request 802 in thecontrol region, e.g., utilizing the PUCCH. In response, the schedulingentity (e.g., eNB) may determine a suitable resource allocation 804 forthe requesting subordinate entity based on a variety of factors orparameters. For example, the scheduling entity may consider the networkloading or how occupied the common UL burst is with other users'transmissions; the nature or volume of data the subordinate entity isrequesting to transmit; and the characteristics of the SRS received fromthe requesting scheduling entity. The scheduling entity may transmit ascheduling grant 806 utilizing any suitable transmission channel andformat to the subordinate entity to identify the scheduled or allocatedresources within the common UL burst of one or more subframes.Accordingly, the subordinate entity may transmit 808 its UL data in thedata region, e.g., the PUSCH of a common UL burst, utilizing thescheduled resources. In this way, interference or collisions betweensubordinate entities configured to transmit utilizing the decoupledmode, which may be relatively high-power transmissions, may be reducedor eliminated.

On the other hand, unlike the data transmissions on the PUSCH within thecommon UL burst 518, the SRS and control transmissions (e.g., ACK/SR) onthe PUCCH within the common UL burst from different users may share thesame time-frequency resources and need not necessarily be scheduled.This is because the control transmissions and SRS may bepower-controlled by the scheduling entity. That is, with suitable powercontrol and in some examples interference cancellation techniques, theSRS and control transmissions from different users may simply besuperposed over one another, and the scheduling entity may still becapable to receive and decode their respective transmissions. In someexamples, these shared SRS/PUCCH transmissions may be differentiatedfrom one user to another by configuring each user or subordinate entityto apply different scrambling sequences or codes to their transmissions,so that the resources are shared utilizing code division multiple access(CDMA). Accordingly, the receiving scheduling entity may be able todifferentiate these users' transmissions utilizing conventional CDMAtechniques known to those of ordinary skill in the art.

Waveforms for the Decoupled Mode

For the SRS, in an aspect of the present disclosure, a single carrierwaveform may be utilized. For example, a single-carrier FDMA (SC-FDMA)waveform as utilized in conventional LTE transmissions, or any othersuitable single carrier waveform may be utilized. That is, within acommon UL burst 518, the SRS may be transmitted both by users that areclose to the scheduling entity, and users that are far from thescheduling entity. In one example, the SRS transmitted by thesedifferent groups of users need not be different waveforms. Accordingly,a waveform may be selected that accommodates any bottleneck that may becaused by users at the cell edge, while providing sufficientfunctionality for users near the cell center. For cell edge users, thesignal power may be relatively weak due to a large path loss. Toincrease the efficiency of the power amplifier for these users, a singlecarrier waveform may be used for the SRS, including those usersoperating in decoupled mode, close to the cell center. That is, use ofsuch a single carrier waveform for SRS transmissions can save power,which may particularly be helpful for users at or near the cell edge.

For the SRS in the common UL burst, a single carrier waveform may beconfigured according to a Zadoff-Chu sequence, as utilized in presentLTE standards and known to those of ordinary skill in the art. In otherexamples, any other suitable pseudo-random sequence may be utilized forthe single carrier waveform in the common UL burst.

In a further aspect of the disclosure, the control region of the commonUL burst 518, which may include the PUCCH, may utilize a discreteFourier transform (DFT)-spread OFDM waveform. Further, the data regionof the common UL burst, which may include the PUSCH, may utilize an OFDMwaveform. That is, the PUCCH and PUSCH may utilize an OFDM waveform,which may include a cyclic prefix (CP) for relatively easy multiplexingof different channels. That is, it can be difficult to multiplexdifferent channels utilizing FDM within the same symbol utilizing asingle carrier waveform. Accordingly, because the common UL burstincludes a symbol wherein the PUCCH and PUSCH are multiplexed, alongwith the DM-RS pilots, aspects of the present disclosure may utilize anOFDM waveform for this symbol or symbols.

The SRS region and the control region (PUCCH) within the common UL burstmay be shared by a plurality of users (e.g., subordinate entities), withmultiple access for these resources being achieved utilizing CDMA, asdescribed above. That is, within the SRS region and the control regionof the common UL burst, users may be differentiated by way of theirrespective use of different sequences in the code domain, with thesesequences being, for example, allocated to the respective users by thenetwork or scheduling entity. Moreover, as described above, differentusers may be suitably power controlled by the network or schedulingentity to further enable reception of each user's SRS/PUCCHtransmissions.

In a still further aspect of the disclosure, the data region (e.g.,PUSCH) within the common UL burst may be shared by a plurality of users(e.g., subordinate entities), with multiple access for these resourcesbeing achieved utilizing OFDMA. That is, within the data region of thecommon UL burst, users may be differentiated by way of their respectiveuse of different frequency subcarriers, with the selection of thesubcarrier or subcarriers to use for their data transmissions being madeaccording to a scheduling grant transmitted to those respective usersfrom the scheduling entity. In some examples, the use of the PUSCH inthe common UL burst for uplink data transmissions may be restricted onlyto users having sufficient power headroom (e.g., available powerheadroom greater than a threshold). Further, the use of the PUSCH in thecommon UL burst for uplink data transmissions may be limited only tousers having uplink payload data that requires low latency (e.g., lowerlatency than would otherwise be available from use of a data region of aregular UL burst, e.g., in an UL-centric subframe).

FIG. 9 is a diagram illustrating a method of operating a subordinateentity for wireless communication over a time division duplex (TDD)carrier in accordance with an aspect of the disclosure. In someexamples, this method may be performed using any of the subordinateentities illustrated in FIGS. 1-4 and 8, or any wireless communicationdevices.

According to the method of FIG. 9, a subordinate entity may utilize acommon UL burst block 320 (see FIG. 3) to transmit a common uplink burstwithin a downlink-centric subframe 902 and an uplink-centric subframe904 on a TDD carrier. For example, the subordinate entity may utilize aDL-centric subframe block 322 to prepare and transmit a common uplinkburst 518 in a DL-centric subframe 504 (see FIG. 5). For example, thesubordinate entity may utilize an UL-centric subframe block 324 toprepare and transmit a common uplink burst in an UL-centric subframe 502(see FIG. 5). The common uplink burst may be the same as the common ULburst 518 described in relation to FIGS. 5-7. For example, the uplinkburst may be transmitted in each of the DL-centric subframe andUL-centric subframe (e.g., frame 500 of FIG. 5). In other examples, thecommon uplink burst may be transmitted in any desired number (e.g., morethan 50% of total subframes) of subframes including DL-centric subframesand UL-centric subframes to provide more UL transmission opportunity.

The uplink burst includes a first symbol that includes a soundingreference signal (SRS) configured to enable sounding of the TDD carrier,and a second symbol that includes information bits and a demodulationreference signal (DM-RS) similar to those illustrated in FIGS. 6 and 7.The DM-RS is configured to enable demodulation of the information bits(e.g., PUSCH) carried within the second symbol. The SRS and DM-RS may beprecoded differently. For example, in FIG. 10, the subordinate entitymay utilize a precoder 1000 to apply a first precoding matrix 1002 tothe SRS, and apply a second precoding matrix 1004 that is different fromthe first precoding matrix 1002 to the DM-RS. The separate precoding ofthe SRS and DM-RS allow control and/or data information to betransmitted utilizing multiple input multiple output (MIMO).

It is to be understood that the specific order or hierarchy of steps inthe methods disclosed is an illustration of exemplary processes. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the methods may be rearranged. The accompanyingmethod claims present elements of the various steps in a sample order,and are not meant to be limited to the specific order or hierarchypresented unless specifically recited therein.

As those skilled in the art will readily appreciate, various aspectsdescribed throughout this disclosure may be extended to any suitabletelecommunication system or systems, network architectures, andcommunication standards. By way of example, various aspects may beapplied to UMTS systems such as W-CDMA, TD-SCDMA, and TD-CDMA. Variousaspects may also be applied to systems employing Long Term Evolution(LTE) (in FDD, TDD, or both modes), LTE-Advanced (LTE-A) (in FDD, TDD,or both modes), LTE-U, CDMA2000, Evolution-Data Optimized (EV-DO), UltraMobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Ultra-Wideband (UWB), Bluetooth, and/or other suitable systems,including those described by yet-to-be defined wide area networkstandards. The actual telecommunication standard, network architecture,and/or communication standard employed will depend on the specificapplication and the overall design constraints imposed on the system.

Within the present disclosure, the word “exemplary” is used to mean“serving as an example, instance, or illustration.” Any implementationor aspect described herein as “exemplary” is not necessarily to beconstrued as preferred or advantageous over other aspects of thedisclosure. Likewise, the term “aspects” does not require that allaspects of the disclosure include the discussed feature, advantage ormode of operation. The term “coupled” is used herein to refer to thedirect or indirect coupling between two objects. For example, if objectA physically touches object B, and object B touches object C, thenobjects A and C may still be considered coupled to one another—even ifthey do not directly physically touch each other. For instance, a firstobject may be coupled to a second object even though the first object isnever directly physically in contact with the second object. The terms“circuit” and “circuitry” are used broadly, and intended to include bothhardware implementations of electrical devices and conductors that, whenconnected and configured, enable the performance of the functionsdescribed in the present disclosure, without limitation as to the typeof electronic circuits, as well as software implementations ofinformation and instructions that, when executed by a processor, enablethe performance of the functions described in the present disclosure.

The previous description is provided to enable any person skilled in theart to practice the various aspects described herein. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects. Thus, the claims are not intended to be limited to theaspects shown herein, but are to be accorded the full scope consistentwith the language of the claims, wherein reference to an element in thesingular is not intended to mean “one and only one” unless specificallyso stated, but rather “one or more.” Unless specifically statedotherwise, the term “some” refers to one or more. A phrase referring to“at least one of” a list of items refers to any combination of thoseitems, including single members. As an example, “at least one of: a, b,or c” is intended to cover: a; b; c; a and b; a and c; b and c; and a, band c. All structural and functional equivalents to the elements of thevarious aspects described throughout this disclosure that are known orlater come to be known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the claims. Moreover, nothing disclosed herein isintended to be dedicated to the public regardless of whether suchdisclosure is explicitly recited in the claims. No claim element is tobe construed under the provisions of 35 U.S.C. § 112(f), unless theelement is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited using the phrase “stepfor.”

What is claimed is:
 1. A method operable at a subordinate entity forwireless communication over a time division duplex (TDD) carrier, themethod comprising: transmitting an uplink burst within adownlink-centric subframe and an uplink-centric subframe on the TDDcarrier, wherein the uplink burst comprises: a first symbol comprising asounding reference signal (SRS) configured to enable sounding of the TDDcarrier; and a second symbol comprising information bits and ademodulation reference signal (DM-RS), wherein the DM-RS is configuredto enable demodulation of the information bits carried within the secondsymbol.
 2. The method of claim 1, further comprising: applying a firstprecoding matrix to the SRS; and applying a second precoding matrix,different from the first precoding matrix, to the DM-RS.
 3. The methodof claim 1, further comprising: applying a scrambling code to the SRS,the scrambling code configured to enable code division multiple access(CDMA) among a plurality of subordinate entities.
 4. The method of claim1, wherein the first symbol of the uplink burst is configured with asingle carrier waveform; and wherein the second symbol of the uplinkburst is configured with an orthogonal frequency division multipleaccess (OFDMA) waveform comprising a plurality of subcarriers.
 5. Themethod of claim 4, wherein the TDD carrier comprises a plurality ofresource blocks, each resource block comprising time-frequency resourcesincluding a set of subcarriers; wherein the SRS in the first symbol ofthe uplink burst spans all of the subcarriers within a resource block onthe TDD carrier; and wherein the second symbol of the uplink burstfurther comprises a control region spanning a first portion of thesubcarriers within the resource block on the TDD carrier, the firstportion of the subcarriers being less than all of the subcarriers. 6.The method of claim 5, wherein the second symbol of the uplink burstfurther comprises a data region spanning a second portion of thesubcarriers within the resource block of the TDD carrier, first portionand the second portion together being less than or equal to all of thesubcarriers.
 7. The method of claim 6, wherein the control regioncomprises a scheduling request (SR) configured to request from ascheduling entity an allocation of time-frequency resources in asubsequent uplink burst, the method further comprising: receiving ascheduling grant from the scheduling entity in response to the SR, thescheduling grant indicating a grant of the time-frequency resources inthe subsequent uplink burst.
 8. The method of claim 7, furthercomprising transmitting the subsequent uplink burst in one of anuplink-centric subframe or a downlink-centric subframe on the TDDcarrier, the subsequent uplink burst comprising data informationutilizing the granted time-frequency resources.
 9. A subordinate entityconfigured for wireless communication over a time division duplex (TDD)carrier, comprising: a processor; a memory communicatively coupled tothe processor; and a transceiver communicatively coupled to theprocessor, wherein the processor and the memory are configured to:transmit an uplink burst within a downlink-centric subframe and anuplink-centric subframe on the TDD carrier, wherein the uplink burstcomprises: a first symbol comprising a sounding reference signal (SRS)configured to enable sounding of the TDD carrier; and a second symbolcomprising information bits and a demodulation reference signal (DM-RS),wherein the DM-RS is configured to enable demodulation of theinformation bits carried within the second symbol.
 10. The subordinateentity of claim 9, wherein the processor and the memory are furtherconfigured to: apply a first precoding matrix to the SRS; and apply asecond precoding matrix, different from the first precoding matrix, tothe DM-RS.
 11. The subordinate entity of claim 9, wherein the processorand the memory are further configured to: apply a scrambling code to theSRS, the scrambling code configured to enable code division multipleaccess (CDMA) among a plurality of subordinate entities.
 12. Thesubordinate entity of claim 9, wherein the first symbol of the uplinkburst is configured with a single carrier waveform; and wherein thesecond symbol of the uplink burst is configured with an orthogonalfrequency division multiple access (OFDMA) waveform comprising aplurality of subcarriers.
 13. The subordinate entity of claim 12,wherein the TDD carrier comprises a plurality of resource blocks, eachresource block comprising time-frequency resources including a set ofsubcarriers; wherein the SRS in the first symbol of the uplink burstspans all of the subcarriers within a resource block on the TDD carrier;and wherein the second symbol of the uplink burst further comprises acontrol region spanning a first portion of the subcarriers within theresource block on the TDD carrier, the first portion of the subcarriersbeing less than all of the subcarriers.
 14. The subordinate entity ofclaim 13, wherein the second symbol of the uplink burst furthercomprises a data region spanning a second portion of the subcarrierswithin the resource block of the TDD carrier, first portion and thesecond portion together being less than or equal to all of thesubcarriers.
 15. The subordinate entity of claim 14, wherein the controlregion comprises a scheduling request (SR) configured to request from ascheduling entity an allocation of time-frequency resources in asubsequent uplink burst, wherein the processor and the memory arefurther configured to: receive a scheduling grant from the schedulingentity in response to the SR, the scheduling grant indicating a grant ofthe time-frequency resources in the subsequent uplink burst.
 16. Thesubordinate entity of claim 15, wherein the processor and the memory arefurther configured to: transmit the subsequent uplink burst in one of anuplink-centric subframe or a downlink-centric subframe on the TDDcarrier, the subsequent uplink burst comprising data informationutilizing the granted time-frequency resources.
 17. A subordinate entityconfigured for wireless communication over a time division duplex (TDD)carrier, comprising: means for transmitting an uplink burst within adownlink-centric subframe on the TDD carrier; and means for transmittingthe uplink burst within an uplink-centric subframe on the TDD carrier,wherein the uplink burst comprises: a first symbol comprising a soundingreference signal (SRS) configured to enable sounding of the TDD carrier;and a second symbol comprising information bits and a demodulationreference signal (DM-RS), wherein the DM-RS is configured to enabledemodulation of the information bits carried within the second symbol.18. The subordinate entity of claim 17, further comprising: means forapplying a first precoding matrix to the SRS; and means for applying asecond precoding matrix, different from the first precoding matrix, tothe DM-RS.
 19. The subordinate entity of claim 17, wherein the TDDcarrier comprises a plurality of resource blocks, each resource blockcomprising time-frequency resources including a set of subcarriers;wherein the SRS in the first symbol of the uplink burst spans all of thesubcarriers within a resource block on the TDD carrier; and wherein thesecond symbol of the uplink burst further comprises a control regionspanning a first portion of the subcarriers within the resource block onthe TDD carrier, the first portion of the subcarriers being less thanall of the subcarriers.
 20. The subordinate entity of claim 19, whereinthe second symbol of the uplink burst further comprises a data regionspanning a second portion of the subcarriers within the resource blockof the TDD carrier, first portion and the second portion together beingless than or equal to all of the subcarriers.